What a difference a year – an eternity in geopolitics – makes. No one could see this coming; the ideological matrix of all strands of Salafi-jihadi terror – which Russia fights no holds barred, from ISIS/Daesh to the Caucasus Emirate – beating a path to the Kremlin and about to embrace Russia as a strategic ally.
The House of Saud was horrified by Russia's successful campaign to prevent regime change in Syria. Moscow was solidifying its alliance with Tehran. Hawks in the Obama administration were imposing on Saudi Arabia a strategy of keeping oil prices down to hurt the Russian economy.
Now, losing all its battles from Syria to Yemen, losing regional influence to both Iran and Turkey, indebted, vulnerable and paranoid, the House of Saud has also to confront the ghost of a possible coup in Riyadh against Crown Prince Mohammad bin Salman, a.k.a. MBS, as Asia Times reported. Under so much pressure, who're you gonna call?
The ultimate ghostbuster; Russian President Vladimir Putin.
Essentially, the House of Saud is obsessed by three main vectors; low oil prices; Iran and Shi'ism; and what to make of US foreign policy under Trump. Let's take them one by one.
I want my S-400s
As much as a Moscow-Washington reset remains doomed, even with the implosion of Russia-Gate, House of Saud advisers must have known that the Kremlin won't ditch its strategic relationship with Iran – one of the key nodes of Eurasia integration.
Moscow will keep aligned with Iran across "Syraq"; that's part of the "4+1" (Russia-Syria-Iran-Iraq, plus Hezbollah) alliance in the Levant/Mesopotamia, an incontrovertible (and winning) fact on the ground. And that does not preclude Russia's increasingly cozy relationships across the Arab world – as with Egypt, Jordan, the UAE and Libya.
What concerns Moscow, deeply, is Saudi (formal or informal) financing of Salafi-jihadi outfits inside Russia. So a high-level line of communication between Moscow and Riyadh works towards dissipating any misunderstandings regarding, for instance, jihadism in Tatarstan and Chechnya.
Moscow does not buy the much-spun (in the West) Iranian "aggressive behavior" in the Middle East. As a key negotiator of the Joint Comprehensive Plan of Action (JCPOA), Russia very well knows that Iran's ballistic missile program is actually the key target of Trump's imminent decertification of the Iran deal.
These missiles actually represent dissuasion against any possible US attack, "leading from behind" or not. The Islamic Revolutionary Guards Corp (IRGC) in Tehran has made it quite clear the ballistic missile program does not fall into the JCPOA, and will remain active.